Artificial denture



R. J. DONAVAN ARTIFICIALDENTURE Dec. 30, 1952 4 Sheets-Sheet 1 Original Filed April 17, 1951 INVENTOR.

Dec. 30, 1952 R. J. DONAVAN ARTIFICIAL DENTURE 4 Sheets-Sheet 2 Original Filed April 17, 1951 INVENTOR.

4rraeMs s.

Dec. 30, 1952 J, DONAVAN Re. 23,607

ARTIFICIAL DENTURE Original Filed April 17, 1951 4 Sheets-Sheet I5 Z INVENTOR. easier .1 paw/44W Dec. 30, 1952 J, DONAVAN Re. 23,607

208527 J. 00AM 1/4/14 Reissued Dec. 30, 1952 UNITED STATES PATENT OFFICE ARTIFICIAL DENIUBE Robert J. Donavan, Mason City, I ll.

Original No. 2,598,769 dat No. 221,415, April 17, 19

ed June 3, 1952, Serial 51. Application for'rereissue specification;

This invention appertains to improvements in artificial dentures, either anatomical or mechanical, and has reference more particularly to the construction of false teeth as used in artificial dentures, either in the form of a whole plate, partial plate or bridgework.

The primary object of this invention is to provide artificial dentures, which have approximately the same grinding and cutting efficiency for food mastication as that of natural teeth, due. to the design and construction of the occlusal surfaces of the molars and bicuspids.

A further object of this invention is to obtain maximum cuspal or ridge contact between the occlusal surfaces of the posterior teeth of the upper and lower dentures, the maximum contact permitting proper mandibular movements (anterior-posterior and lateral excursions) with a minimum of cuspal interference.

A further object of this invention is to improve the cutting and grinding efficiency of the occlusal surfaces of the teeth of artificial dentures by providing unique mechanisms on the occlusal surfaces of the molars and bicuspids and by, providing a more extensive horizontal occlusal surface for the posterior teeth.

A further object of this invention is to provide armoured cusps on the occlusal surfaces of the posterior teeth, the armoured occlusal surfaces reducing to a minimum the wearing away and breakdown of the occlusal surfaces of the teeth and preventing loss of vertical dimension, especially in plastic teeth, while also preventing the chipping of the teeth or breaking up of portions ofthe cuspal walls, especially in porcelain teeth.

Still further objects of the present invention reside in the details of construction of the individual teeth and in the construction and relationship of the occlusal surfaces of the upper and lower posterior. teeth which insures their greatest biting and masticating efiiciency, and the least possible liklihood of cuspal interference, incident chipping of the teeth or displacement of the plates from proper position within the mouth and prevents an imposition of deleterious strain onv the mucous tissues or imposition of direction upon the mandibular motion.

These and ancillary objects and structural features of merit are attained by this invention, the preferred embodiments of which are set forth n t following d c ption and illustrated in the accompanying drawings, wherein:

Figure 1 is an occlusalsurface view of upper and lower artificial dentures including teeth constructed in accordance with the principles of the present invention;

in the original patent but forms no part oi this matter printed in italics indicates the additions made by. reissue.

Figure 2 is a fragmentary perspective view of the posterior portionsof one side of the upper [and lower dentures, from the lingual side with] and lower dentures, from the buccal side with the dentures in occlusive relationship;

Figure 3 is an enlarged perspective view of the posterior teeth on one side of the upper denture with the teeth shown in inverted position;

Figure 4 is an enlarged perspective view of the posterior teeth on one side of the lower denture;

Figure 5' is a transverse cross sectional view taken on line 5- 5 of Figure 3 and illustrating the first molar in cross section to more particularly depict the cuspal arrangement and formation of the occlusal surface;

Figure 6 is a transverse cross sectional view taken on line B6 of Figure 3 and illustrating in cross section the first bicuspid the cuspal and rid e formation being shown in detail;

Figure 7 is a transverse cross sectional view taken on line 11 of-Figure 4 and illustrating more particularly the bucco-lingual ridge formed on the occlusal surface of the first molar;

Figure 8 is a transverse cross sectional view taken on line. 8 8 of Figure 4 and illustrating more particularly the formation of the occlusal surface of the first bicuspid of the posterior teeth of the lower denture;

Figure 9 is an occlusal surface view of an upper and a lower artificialdenture of modified form in which the occlusal surfaces are formed with armoured cusps;

Figure 10 is an enlarged perspective View of the mating occlusal surfaces of the molars of the upper: and lower artificial dentures;

Figure, 11 is a transverse cross sectional view, showing more particularly the engagement between the cusps of the upper and lower molars;

Figure 12 is an occlusal surface view on an enlarged scale of one of the molars of the upper denture, illustrating in detail thearrangem ent and formationoftlie cusps; P

Figure 1 3 is a fragmentary occlusal surface View of one. side of the upper denture;

Figures lfi, 14a and 1,410. are cross-sectional views, illustrating in diagrammatic form the relationship between the upper and lower dentures, when in position in the oral cavity and during masticating movements to depict the relationship between the occlusal surfaces, during mandibular motion, the dentures being shown in concentric, protrusive and extrusive positions;

Figure 15 is an occlusal surface view of a posterior mot 0f t e upper denture having a modifi d form f 1 1 ar a em Figure 16 is a transverse cross sectional view taken on line l6-l6 of Figure 15.

For a morelucid understanding of the present invention, it will be generally recognized that artificial or false teeth, in the form of the whole denture or plate, are relatively low in efiiciency for the mastication of food, when compared with the high degree of efiiciency of the full set of natural teeth. The comparative low efliciency of the average set of dentures is essentially due to the anatomical aspect of the teeth, since, for esthetic reasons, those skilled in the prosthetic art have made false teeth to resemble as nearly as possible natural ones. In the provision of such false teeth, insufficient consideration is eX- tended to the efliciency of the teeth during mastication of food. Whereas natural teeth are securely set in the bony structure of the jaw and, therefore, have a very high pressure range artificial teeth, on the other hand, must find their bearing surfaces upon the tender mucous tissues instead of in the bony tissues and do not have a firm anchorage in the mouth. The limitations in afiording proper bearing surfaces for the artificial teeth prevent the attaining of high masticating pressures.

Since artificial dentures must occupy the same position, as nearly as possible, in the oral cavity, it is obvious that any increase in efficiency must necessarily come through an improvement in the design of the occlusal surfaces of the teeth, so that the artificial dentures may find their greatest efliciency in a grinding and cutting engagement of the occlusal surfaces.

Any improvements of the cutting edges and occlusal surfaces of the artificial teeth must necessarily be limited to the posterior teeth, due to the fact that the anterior teeth are visible to the casual glance of a layman and, for esthetic reasons, should have a natural appearance. Furthermore, the posterior teeth are of greater importance in the mastication of food than the anterior teeth and the improvement therein to increase grinding or crushing efficiency of the teeth with a more natural movement of the mandible or jaw is the primary purpose of the instant invention.

In accordance with the object of the instant invention, the cutting edges of the posterior [teeth or the dentures are improved. while con-J teeth of the dentures are improved, while consideration is also extended to the prevention of interference between the occlusal surfaces of teeth of the opposite dentures and to the obviation of interference with mandibular motion. It

is, therefore, the primary aim and purpose of the instant invention to provide substantially the same grinding and cutting efiiciency as that of natural teeth for food mastication by improving the design and construction of the molars and bicuspids of the artificial dentures.

As can be appreciated, it impossible to establish fixed paths of movement for mandible action, since the actions of the mandible during mastication vary considerably in each person. In each individual, the paths of motion of the mandible are controlled by Various factors and artificial dentures must be constructed to conform to the corresponding path of movements, rather than to set up and establish a radically different path of movement, which, of course, would result in considerable interference with the mandibular action and would cause deleterious strain on the jaws and gum tissues. The artificial dentures, provided by this invention,

do not interfere with the movement of the mandible anteriorly, posteriorly or laterally at any angle, though a slight interference with the mandibular is encountered in a downward slanting motion, in its lateral movements. However, the latter interference is natural and does not work any strain on the mandible.

The foregoing object is accomplished by providing a multiplicity of cuspal and ridge contacts, the mandible moving freely, without being locked by inclined planes of opposing cusps or guided into preconceived paths by grooves or other mechanical devices on occlusal surfaces.

More specifically, the number of cusps on the premolars and molars of the upper dentures or plates are increased and the cuspal and ridge design of the bicuspids and molars of the lower plates are changed and extensively modified, especially with reference to the provision of a novel bucco-lingual ridge structure. Furthermore, the cusps of the upper multi-cusp teeth are of rounded, partly globular form and themrangement is modified so that sliding contact with the occlusal surfaces of the lower posterior teeth can be effected.

Referring now more particularly to the drawings, attention is directed to Figure 1, where the [upper and lower plates for dentures are illus-J upper and lower plates or dentures are illustrated in plan view, the dentures having teeth set therein which are made in accordance with the details and objects of the present invention. The upper plate In and the lower plate 12 may be molded in the usual manner, and may be formed of any of the materials now in general use and the teeth which are set in plates may be of porcelain, or a molded material, such as acrylic or any other plastic, which would be satisfactory from a point of durability, efliciency, color and capability of being molded to desired shapes.

Themanner of forming the plates and teeth is immaterial, except that the teeth should be permanently united with the plates, so as to avoid any possibility of their displacement therefrom in use and the teeth should, of course, be set in accordance with the natural tooth arrangement of the patient, the size and shape of the teeth being determined thereby.

In Figure 3, the occlusal surfaces for the bicuspids and molars of the upper plate Ill is illustrated in detail, the occlusal surfaces of the posterior teeth 14 and I6 of the upper plate being modified and being designed and constructed in view of the same principle. The anterior teeth 8 may be formed in the conventional manner and should resemble, as nearly as possible, the natural teeth'of the patient.

The occlusal surfaces of the first bicuspid I8 and the second bicuspid 20 are similarly formed, as are the occlusal surfaces of the first molar 22 and the second molar 24. The occlusal surfaces of these teeth are so constructed as to contain a group of mechanical semi-globular or semi-cylindrical cusps 25. In Figure 3, four cusps are provided for the bicuspids l8 and 20 and seven cusps for the first and second molars 22 and 24. However, any number of cusps may be formed, dependent upon the size of the area or space containing the cusps and the size of the cusps. The number or size of the cusps is not of critical importance but the shape and specific formation and arrangement thereof on the crown of the teeth constitutes one of the important aspects of this invention.

38; icu pi s; being im larln formed: with.

distal marginal: borders, 4.0.; and: mes-lat: marginal borders 42-; The mesialz and-1 distal. mar ina borders of: both; the, hicuspids and; molars are; so constructed as. t be; well; belowt e: tips; Qfi the cusps 26.

The; occlusal. suriaces at. that bicusridsz 1 82 2.0: are; defined bythe; line lin ual mechanical: cusp chemical; cusps: 48,; t is uceal hail 50 and the conventional buccali. cusps- 5. semilobularrcusps 25' areas arran ed. ha lingual mechanical-1101151146; eszediaceht- .Q; lingual. uspand: the; bucoal: mechanical: c sp 5.0: is disposedi adjac n t the: onv ntional buccal' cus 52,, the cusps; and. illl cingz in a i ns that th rareinterseet dby-thev buccor-lingual; ridge. The natural cusns:4 l.=-an.d:5-2 and the mechanical: cusps; groupedi in: a; specifie cally arranged pattern within: the natural bwuccal nd lingual; cusps. are so: arranged; that: when viewed: from. either. the mesial; or distal; side: of the tooth, the buccal: cusps. 5.2 are Off the: great;- est height, with the conventional; lingual cusp 44-: being; next: in; height. Thev buocal': incchanir cal cusp 50 is: third; highest with. the; lin ual mechanical cusp: being; fourth; in, height aildi the central mechanic l; cusps 4.8:- lyin welt elow he plane, or; the tips;- or crests of the: lauccal and lingual meehanicalcu s 5.0; nd 4.6:.

The elevation: or: arran ement of the: usp

can; beparticularly discerned: Fi ure. 6, wh rein it; will" be noted hat: thecon entional buccal: cusp 5.2: is s bs. n.:ti -llr hi her the convention l..- lin al 1 1% 44-, with the; buccal mechanical. cusp: 5n ly n elow the conventional buccal and lingual, cusps, and; lying abojvethe lingual, mechanicali cusp: 46', which extends above the central mechanica-lcusp: 4:8;

The occlusalsurfaces of the: ,rnolar; are, con.-

structedin asimilar manner, in thelingual ps 54 and. uccal; cusps: conventional; in; f buccal cusps bein the, his

olusal surtace-otthemma. c Q

lingual. cusps 5.4;, as seen Qgurc; 5.. Th... of; buecal mechanical opens 58.; no in height. and lie-1 below,- the; lingnal; andi bu cal cusps.- The lin ual, mechanical. cu ps (innat formed in a manner similar to, the formation-of 56 are substantially the. buccal' mechanical: cusps 58;. and lie below the plane. of the, buccal. mechanical, cusps, the cusps 58, and 60; following: theslanting, pattern ofthe conventional lingual and: wel. usps and. being arrang d. with, the central mechanical cusps 62,. which are the. lowest cuspson thaocclusal suriace, so that. the tips of.v the... cusps lie on the arc. Aa-B, viewed. from. the distal- Side of, the tooth. and the line, A E being. struck along the paced-lingual ridge. Similarly, the

tips of the cusps for the. bicuspids, seen- Figure 6,..lieso. that they are in. an arcuate pattern...

As. seen in Figure 13,. the. cusps. of. the, pro.- molars. and themolars; are. arrangedso that. the

[nuccal .niechanical; cusps of. the hi roov s; levation: and

cu ps-are-in er ct d by which parallels the line; A'.B'-]

. bucccLmeohanical cusps of the. m l rs and; i.

cusm' s rare intersected, by a straight Zine A".-'-B" which is: extended. adistal-.mesicl direction. The central; mechanical cusps; are intersected by munch- RH; which parallels theline A" and the lingualv mechanical cusps ofthe molars andbiscuspidslieon a lineA?-B3. The lingual, huccalcand central mechanical cusps are thus ar-. ranged. along straight parallel lines, A'-.-B AK/ -B" and. 53-43 therma l in s n n relation-to. the nte or-po ter or m on o the mandible and; 11. 11s, th r angement. of. he

relation. o.- aht ri rrnosr th arch X: Th os ono ted, in. Figure 1: inthe. oral w ll. posi i hem hani a were al ne straight spaced apart-.- ines wh ch. ub tanially paral el o. each: o h r; h in ersec in lines Y-Z showing the arrangement of the cusps f lat ral; mot n:

Infligurelz the oeclusalsurface of the molars, is; more 01631-13? illustrated; the buccal mechanical cusps fiflheing formed in apair-Gil, 6!. Each of thecuspsofthepair is spaced apart andis of the same height, theheight of. the -cusps, inrelation to the other mechanical cusps, being greater, while the thr'eelcentral mechanical cusps:6 2 are the lowest,.on the occlusalsurface. The central mechanicalcusps 62-, 63 and 63? are of the same height, withthc lingual mechanical cusps 58' and 59 being, slightly above the central cusps 62 and slightly below the buccal cusps 60. The bucca-l cusps are arranged in a pair, each of the cusps being aligned from a bucco-lingual direction, wit the; n ual me h ical c Thecusps 581,541 and 62 of the buccal, lingual; and. central mechanical formations form an arcuate broken ridge O--P,- onthe mesial sideof thctooth, while the cusp 63 formswith the distal marginal bo de a r ken ara ridge M.-N. the centerH and B of the ridges being in alignment on, the line A "-Bf, which parallels the anterior-posterior direction of movement of the mandible; The cusps 59', 63' and GI form a broken ridg-e-DF, with the center E on the line A"-B-" and thecenters. of the ridges beingat the, centers. of the central mechanical cusps, The cusps of the i usds and the m a s. a d d n. F gure 13;. he.-

the; pa al elt isht li e nd sps; of. each indiv d a t o h. i p ed on the. ar uatelihcs t d fine the: b ok n... d es across heo clusalsurr a ott to T e:.t. s i crests; of the usps-m k sl d Contact wit theccclusa-l surfaces-o the lower posterior teeth and carry the Weight of occlusalcontact and mandibularmovement, (lateral, anterior and posterior) in all directions and at all: angles, without forcing the mandibular into any-preconceived paths,

modified-cusp formation is illustrated, wherein the ridges 54,, 66 and 68;, lying on the. arcs. OBB; DEF and MHN, are unbroken. The individual cusps are illustrated in dotted lines. but the ridges are unbroken instead of broken, as in Figure 12. A. tooth, constructed as illustrated in, Figure 15, would make the mandibular moyements. smoother and. would have a better slidingengagement with the .occlusal surfaces of the lower posterior tooth, due to. the absence oi" sulci, between the individual. cusps and extendinsq roni themes al o the: distal side.- Al

the occlusal surface ofeach' molar,

of the posterior teeth of a denture could be constructed in this manner or only the first molar may be so constructed, the first molar forming the bearing tooth for the teeth. The specified height relationship of the mechanical and conventional lingular and buccal cusps would be, of course, preserved, with the portions of the ridges, lying between the cusps conforming thereto.

As seen in Figure 16, which is a cross sectional view of Figure 15 looking toward the distal side of the molar, the ridge 66 is defined by the cusps of the central mechanical, lingual mechanical and buccal mechanical sets, with the spaces between the cusps filled in and properly dimensioned and leveled, so as to retain the same elevational relationship between the cusps, as illustrated in Figure 5. Thus, the cusps El, 63' and 59, which lie on the line DEF, are in the same elevational interrelationship and relationship [with the conventional buccal cusps 34 and conventional lingual cusps 32] with the convertticmal buccal cusps 32 and conventional lingual cusps 34.

In Figure 11, the upper molar 22 is shown in cross section, from a line transverse to the anterior-posterior direction of movement of the mandible and the arrangement of the cusps, with respect to the buccal surface of the molar onthe lower denture can be ascertained, the line C-D showing the inclination of the upper and lower teeth, from the vertical plane.

Attention is now directed to Figure 4 and the sectional illustrations, taken from Figure 4, wherein the posterior teeth of the lower denture are illustrated, including the pair of premolars or bicuspids I2 and I4 and the first and second molars I6 and 18. The occlusal surfaces of the lower bicuspids and molars have been designed and constructed for proper engagement without cuspal or ridge interference, with the cusps on the posterior teeth of the upper denture or plate. The bicuspids 12 and I4 are formed bucco-lingually by massive sized bucco-lingual ridges 80 and 82, the ridges being of a size to substantially span the spaces between the tips or crests of the multi-cusps on the occlusal surfaces of the upper posterior teeth, so that a smooth and yielding passage to the mandibular action is provided. The bicuspids and molars of the bottom plate or denture, when viewed from a buccal or lingual direction, present the same contours, grooves, elevation and angles as a naturaltooth. The first and second bicuspids Hand 12 are formed with the distinct lingual'cu's'ps 84 and Stand with distinct buccal cusps 88 and 90, all of thecusps being blunt and massive. There are no high or sharp points on the cusp's, the wear surface of the cusps being rounded or rolled, as [seen in Figure 8. The lingual cusps 82 and 84] seen in Figure 8. The lingual cusps 86 and 84 are reduced in size as compared with the buccal cusps 38 and 90.

The buccal cusps 92 and the lingual cusps 94 on the first and second molars are defined by the buccal and lingual grooves and depressions on the buccal and lingual surfaces, with the lingual cusps being reduced in size as compared with the buccal cusps. Both the buccal and lingual cusps are formed so as to merge and form two ridges 93 and 95 extending from the mesial to the distal on, the buccal and lingual sides of the occlusal surfaces, the ridges replacing the cusps and being massive in design. The buccal and lingual ridges are .united by the massive bucco-lingual ridge 96 on the buccolingual ridge crossing the occlusal surfaces in a bucco-lingual direction, slightly mesial to the bu'cco-lin'gual axis of the occlusal surfaces.

The point of eminence for the occlusal surfaces of the second bicuspid and the first and second molars, is located on the bucco-lingual ridges, 82, 96 and 98, on the mesial-distal center of the bucco-lingual ridge slightly buccal to the mesialdistal axis for the occlusal surfaces. From this point of eminence I00, as seen in Figure '7, the occlusal surfaces slope downward in all directions, rapidly mesially and distally to form the mesial and distal sulci systems, and slightly buccally and lingually to form the crest of the buccal and lingual ridges.

The occlusal surfaceof the lower first bi'cuspid 14 is different from'that-of the second bicuspid and first and second molars, inasmuch as'the [point of eminence I02 on the tip of"the buccal ridge 84, as seen in Figure 8, is more to the'lingual] point of eminence 102 on the tip 'of the bucco-lingual ridge 80 as seen in Figure 8 is more to the lingual side. The bucoo-lingual ridge 80 crosses the surface in a bucco-lingual direction from the high point extending downward to the center of the surface, where it is crossed by the connecting sulcus I'M, as seen in Figure 4, the sulcus extending mesially and distally to unite the two sulci systems 106 and 108.

eral movement of the mandible.

It will be noted that the high point on the bucco-li'ngual ridges of the occlusal surfaces of the bicuspids and molars of the lower posterior teeth are higher than any other point on the occlusal surfaces. The specific formation of the bucco-lingual ridges, with the point of eminence of the occlusal surface formed thereon, assists in giving a downward slanting direction to the lat The buccolingual ridges, together with the buccal and lingual ridges and the massive cusps on the first and second bicuspids pass freely through the arc K-L, in Figure ll, the crests or tips of the multicusps on the upper bicuspids and molars being located on the arc at all directions and "at all angles. The multi-cusp teeth of the'up per arch meet the massive ridges and cusps of the lower teeth in tip to tip multiplicity of contact, which presents greater mincing effect to the masticating action with less harm to the underlying soft mucous tissues and bony supporting structures. The contact, in lateral motion, between the oc clusal surfaces of the posterior teeth will be a sliding and a somewhat guiding contact to the extent that the lateral mandibular motion has imposed upon it a downward slanting direction but no other. This contact will obvi'atethe harsh, crushing and-interlocking meeting or the more or less flat inclined planes of the cusps of the conventional teeth. The inclined planes of the cusps of conventionalteeth present great interference to lateral mandibular motion and in addition tendto impose direction along certain definite paths. 7 Of course, rounded surfaces can pass more readily over each other than can more or less'fiatsurfaces and since the contact surfaces of the teeth of this invention are rounded, and since there is a-multiplicity of contact between the cusps and ridges of the opposing dentures,

the mandibular motions will be greatly freed of impediments or obstacles.

It will be noted that the bucco-lingual ridge d8, as seen in Figure 11,. is substantially arcuate in cross section, the point of eminence l00 for the occlusal surface being on the bucco-lingual ridge slightly mesial to'the bucco-lingual axis of the occusal surface. The bucco-lingual ridge does notform-or defineanycusps and is-not on-atrue are, as seen in Figure 8, in "order'to form the point of eminence I02.

The first and second bicuspids l4 and 12 have the distinct buccal and lingual cusps 88, MAB-and 90. 'The cusps are blunt and massive and not-high or sharp, with the lingual cusps being much smaller thanthe buccal cusps. Each tooths' occlusal'-'surfaceis crossed in a' bucco -lingual direction' by the bucco-lingual ridges.

"In the denture I2,'the-Tfirst'and second biscuspids 14 and 120i the posteri'or-teeth are-so arranged that the 'lingual' cusps 84-and 8li are: free from contact with the multi cusp:occlusalsurfaces of the first andsecond posterior teeth of.'the upper set, when the mandible is in'--anterior-1-posterior or lateral motion. The'contact of ztheifirst and second bicuspids with the upper posterior teeth is on the buccal cusps and the bucco-lingual ridge of thesec-ond biscuspid. flhese blunt cusps and the'massive ridge bear-the 'weightro'f contact with the multi-cusp upper posteriorteethatimany points and permit the anterior, posterioriand lateral excursions ofithezmandible -withaax minimum [of cuspalinterference. :The buccalxridgefiZiis much larger than the lingual ridgeifl and occue] of cuspa-Z interference. The l biuccal ridge 1.93 1 is much. larger than the lingualsridga 95-. and occupies a position ofslightlygreater"height. The buccal and lingual ridges are made in more or less the shape of'sa segment of; a cylindrical: body; from the 'me'sial "and :distal raspects. These massive buccal and lingualzridges, ofimore: or; less: cylindrical shape, when in contact with themulti cusps occlusalsurfaces of theJuppLer posteriorxteeth,:present amultipl-icity 'o'f;:contact, which reduces cuspal interference" to :a sminimum .-.in the anterior, posterior and lateraliexcursions ofcthertmandible. The massive bucco -lingual i ridges of .the: second bicuspid and first andrsecondxmolars, Jon which arethe high pointsof thesezocclusal surfaces;'presents a slanting downward directionttdthecmotion of the mandible: in, its lateral1:excursions:andassists; greatly in anterior-and .posteriortmovements.

The vfirst bicuspi'ds, :the second :tbicuspi'ds, sand the'first andsecondmolars: have two distinct sulci systems,.'-mesial an'd distal. i'Tl'IB' sulci isystems'tof the first :bicuspids are difierent fromrthose .of the three other teeth. :Inzthecfirstbicuspids,1the.buc-

co-lingual ridge 80 is crossed in amesialedistal-direction .by 1 the connecting :sulcus fiat the lowest point on the i ridge, the sulcusifalling rapidly downward to the 'mesial' and :distal 2' to form the mesial and :distal-fossa. A mesiallingualtandna mesial-buccal sulci is defined by the fossahandia distal-lingualiand a distalrbuccalisulci isdefined, the .sulci. descendingzslowly: to'theirterm-ination at the distal-and mesial bordersiofithe:occlusal :surfaces. presents only two fossae, .a distal .fossa,-:aan.d:a mesial fossa, the sulcicfrom their source descending downward in all partsi-of their. course.

The second bicuspid and the first. and;- second molars'h'ave two distinct.,sulcisysterns on each occlusal surface, the sulcisystemsjheing separated by the bucco-lingual ridge. Thesulci systemsrare alike except that'the distal systems are somewhat reduced insize; so'that a description ofone should be sufilcient system rof 'the'occlusal surface'of the first molar is :as' follows :The :sulci system takes its origin from two pointsmne' buccalto the mesial-distal axis of this surface,- thetother lingual to it; at the junctions of The. occlusalsurface of:.the firstf bicuspicl I for all. For example,"the mesial sulci tion, thetmolars 16 the bucco-lingualridgewith-buccal and lingual ridges. From these points, the sulci extend downward and mesi'ally to themesial-distal axis where they form a junction, just lingual to the axis (the junction being-the mesial-central fossa). This junction is theinception point for a-single sulcus to the mesial'and downward to formthemesial fossa, which defines two sulci downward and to the mesial-lingual and mesi-al-buccal 'to their termination at the mesial-border. The sulci system from its origin to its termination always pursues a'downwardcourse, thesulci formingfour fossae-on the whole occlusal surface as follows, the mesial fossa, the mesial-central fossa, the dista-hcentral fossa and the distal'fossa.

Thus, inthe posterior teeth, theocclusal surfaces are formed, so that there are 'four'fossae on the occlusal'surface of each tooth,'except-the lower first bicuspid has twofossae, andthe iouccvzrlingual ridges are formed, so that the-high; point of eminence is-in the center of the-ridge-and the point of eminence defines "the highest :point on the occlusal 'surfaces'of the bicuspids andmolars. The buccal and lingual ridges areformed; so-that their crests are contoured throughout their'entire lengths,'or thecrestsbeing in a straight line and contoured slightly only'at the ends. The sulci pass downwardly throughout their course from inception to termination.

In Figures'l' l, 14a and 14b, the dentures'iare illustrated, somewhat diagrammatically, in the various mandibular movements. 10f course, the movements of the mandible" vary in eachperson and aregoverned and giventheir course by'things and conditions that-are peculiar to each individual. "Thus,-muscles, fossa bone structure'tissue tolerance and many other factors enter into'the initiation and "determinance of the course and movement of themandible. Every, individual has anterior, posterior-and lateral'movement of the mandible ,andall dentures are constructed," with the movements of the mandible in'min'd.

:InFigure 14, the upper denture plate I1! and lower denture 12 are illustrated" in centric :posion each side of theposterior teethheing illustrated, with the buccoI-lingual ridge" exploited. "The molars of. the upper'denture are illustrated incross section. "The dentures are depicted" in centric occlusion parallel" to. lines CD --and CD which'illustrate'thisposition1in allof [the figures. At' M0,. the, point. of,.eminence v.on the] the figures. kit-120,.the pointofeminence on" the bucco=1ingua1 ridge. of. the molars 'of the lower posteriorteeth is illustrated, the point restingdirectly under one of ;the mechanical cusps .o'f the uppenmolars. Thus, in "Figure 14, the point of eminence isdirectlyin vertical alignment, and underlies "the :crest or .tip of the mechanical cusps 63', so thattheypointjtE overlies'the point "of "eminence 'o'f'the :bucc'o-lingual ridge; the arc DEF transversely "intersecting the point vof eminence at its center. The three central mechanical cusps -=B2, fis andtt, as'seen in'Figure"1 2, are constructed "on each molar so that the -buccolingual ridge on'the lower-molars must be in contact with-oneor"more':of' them'at all timesin onthe upper molars. The larger and more evenly contoured the 'bucco-iingual' ridge .is, "the. more smooth will be the"mandibular-'movements. The arcKL illustrates the'planein' which the crests of the upper cusps lie. Each of the upper molars is-iormed with 1 I cusps, which ideally should all contact the ridges of the 'lower'molars but, due to imperfection in skill and materials, usually only 8 of the cusps will contact the ridges of the lower molar, but, in any event, a multiplicity of cuspal and ridge contact is provided, whereby the occlusal surfaces can pass freely over each other without greatly disturbing interference in mastication.

In anterior-posterior movements, the ridges of the lower teeth would pass freely back and forth contacting the multi-cusps within the arc KL. However, anterior motion would be disturbed the instant the incisal edges of the lower anterior teeth began to mount on the lingual surface of the upper anterior teeth. At this point, balanced occlusion is lost and malocclusion begins and only the retention of the dentures against the underlying mucous tissue holds them in place. Posterior occlusal contact is lost at this point, as the general rule.

In Figure 14a, the mandible is depicted in right [lateral movement, the point I20 or point of emf-1 lateral movement, the point 100 or point of eminence on the bucco-lingual ridge being moved to the right to gain contact with the buccal mechanical cusps and possibly to the conventional buccal cusps. Of course, the latter movement is dependent upon the range of lateral movement and the range of lateral and anterior-posterior movement varies greatly in different individuals.

On the opposite side of the dentures, the point I [of eminence I20 is moved to the right to contact] of eminence 100 is moved to the right to contact the lingual mechanical cusps 60 and the lingual [conventional cusps 54. The whole ridge surfaces] conventional cusps 34. The whole ridge surfaces of the lower posterior teeth will be in contact with the crests or tips of the cusps of the upper teeth, the degree of contact being in accordance with the perfection of the tooth assembly set-up.

This gives a multiplicity of contact which permits movement with great freedom and balanced occlusion in the movements. At the same time that the lateral movement is carried on, the crest of the bucco-lingual ridge is in contact with the upper cups and will guide the mandible along the arc A-B, in which the crests of the upper cusps are located, the mandible being guided to a downward slanting direction in the lateral movement.

In Figure 14b, the left lateral excursion of the mandible is illustrated, the action being opposite to the illustration in Figure 14a, since the point of eminence would contact the opposite cusps, as seen clearly in the figure.

The bucco-lingual ridge on the occlusal surface of the lower bicuspids and molars is an outstanding and important feature of the formation of the occlusal surfaces of the posterior lower teeth, inasmuch as its function is to aid the buccal and lingual ridges of the lower posterior teeth in sliding over the tips of crests of the cusps of the upper teeth, when the mandible is in lateral motion. The ridge performs this office, due to its abundance of contact with themechanical cusps and the four conventional cusps. In anterior and posterior motion of the mandible, the ridge because of its massive construction slides over the tips or crests of the upper mechanical cusps with great case, being too large and massive to fall in the spaces between them and cause interference. Moreover, these occlusal surfaces give extreme freedom to anterior and posterior motion of the mandible, as far as the upper anterior teeth will permit. Interference in anterior and posterior motion in the mandible is due mostly to the lower incisors and cuspids passing forward and downward over the lingual surfaces of the six upper anterior teeth, causing the posterior teeth to lose occlusal contact with each other.

Thus, it can be seen that the multi-cusp teeth will increase masticating efiiciency, since a multiplicity of cusps will be formed on the occlusal surfaces of the upper'posterior teeth and complementary ridges will be formed on the occlusal surfaces of the lower posterior teeth, the ridges mating in sliding and free engagement with the cusps on the occlusal surfaces of the upper posterior teeth. The ridges on the lower posterior teeth take the place of cusps and perform the same masticating function and additional functions, such as increasing the ease of mandibular movements.

The following features are of extreme importance: I

A. Multiplicity of cusps on the occlusal surfaces of the upper posterior teeth and modified bucco-lingual ridges.

B. Modified bucco-lingual ridges on lower teeth for modifying ridge structures.

C. Sulci systems of the occlusal surfaces of the lower teeth, differing from other sulci systems and the fact that from their source they extend downward in all parts of their course.

D. Unique mechanical devices upon the occlusal surfaces of the posterior upper and lower teeth to increase masticating efficiency.

E. The unique mechanical device upon the occlusal surfaces to reduce interference with mandibular motions.

F. A minimum of guided direction imposed upon mandibular motion, the imposed guided direction being only that .of a downward slanting direction to lateral movement.

G. The natural appearance of the teeth from any reasonable area of visibility.

It is to be particularly noted that the buccolingual ridges are semi-cylindrical in shape and the ridges extend from buccal to lingual surfaces in an arc mesially or distally or straight across as the size and shape of the occlusal surface will permit. The bucco-lingual ridge of the lower teeth is massive in design extending straight across the occlusal surfaces and dividing the surfaces into a mesial and a distal area, in which are the unique sulci systems. The straight buccolingual course of the ridge and its point of eminence for the lower occlusal surfaces aids in the proper mastication and in the movement of the lower denture on the upper denture.

In Figure 9, modified denture structure is proof the upper denture are formed and constructed in a manner similar to the construction of the denture, in Figure 1, except that the cusps are covered with metal armour. [The occlusal surfaces may be formed and then covered with a melted metal, which, after setting, would have a wear surface, similar to the occlusal surface of the denture in Figure 1. Or, the porcelain crown may-be formed plain and the armoured cap may be configured, so as to have the cusps formed thereon] The occlusal surfaces of the posterior teeth of the lower denture I26 are formed with the ridge structure and the sulci, as in Figure 1, except that the ridge and sulci are covered with an armour.

It can thus be-seen that the occlusal surfaces of theupper posterior teeth are especially formed with the cusps, arranged and constructed as aforedescribed, and the occlusalsurfaces of the lower posterior teeth are especially formed with the ridge and sulci systems, so that the occlusal surfaces engage in sliding contact and obtain proper mastication, the loss of pressure, such as found in natural teeth, being compensated for by the cutting and grinding action of the mating occlusal surfaces of the upper and lower teeth. Also, the particular formation of the buccolingual ridge and especially, the point of eminence thereon, permits proper mandible motion, without any interference and especially, without imposing any strain or wear on the gum tissues and causing improper seating of the plates.

While the foregoing invention has been especially described and illustrated as related to dentures or full plates, it is apparent that the same can be us'ed'to'full advantage with bridges or individual replacement teeth.

Havi'n'g'thus described this invention, what is claimed is:

1. The combination of upper and lower dentures, each having artificial posterior teeth, the posterior teeth of the upper denture having semiglobular cusps formed on their occlusal surfaces and the posterior teeth of the lower denture having bucco-lingual ridges extending across the occlusal surfaces and adapted to span the cusps on the upper teeth.

2. The combination of upper and lower dentures, each having artificial posterior teeth, the posterior teeth of the upper denture having buccal and lingual cusps and semi-globular mechanical cusps arranged between the buccal and lingual cusp-s, the mechanical cusps on the occlusal surfaces of the premolars and molars of the upper denture lying in parallel planes parallel to the anterior-posterior direction, and the posterior teeth of the lower denture having buccolingual ridges formed on their occlusal surfaces and adapted to span the mechanical cusps on the upper teeth, said ridges defining distinct sulci systems on the occlusal surface of each lower tooth.

3. The combination of upper and lower dentures, each having artificial posterior teeth, the posterior teeth of the upper denture having buccal and lingual cusps and semi-globular mechanical cusps on the occlusal surfaces of the pre molars and molars of the upper denture lying in parallel planes parallel to the anterior-posterior direction, and the posterior teeth of the lower denture having bucco-lingual ridges formed on their occlusal surfaces and adapted to span the mechanical cusps on the upper teeth, said ridges defining distinct sulci systems on the occlusal surface of each lower tooth, said sulci systems lying mesially and distally of the buccolingual ridge and originating from two points, one of said points being buccal to the mesialdistal axis of the occlusal surface and the other lingual to the mesial-distal axis.

4. The combination with upper and lower dentures, each denture having artificial posterior teeth, the posterior teeth of the upper denture 14 having buccai'and lingual cusps and se miglobularmechanicalcusps arranged between the buccal and lingual cusps,'and'the posterior teeth of the lower denture having massive bucco-li'ngual ridges formed on their occlusal surfaces, the ridges each having a-highest point which points define the points of eminence "of 'the occlusal surfaces'of the lower teeth.

5. The combination with upperand lower dentures, each denture having artificial posterior teeth, the posterior teeth'of the upper denture having buccal'a'nd lingualclisps and semiglob'ular mechanical cusp'sarranged between the buccal and lingual cusps, and the posterior teeth of the lower denture having massive bucco-li'ngual ridges formed on their occlusal surfaces, "the ridges having a highest'point 'which'defines" the point of eminence of th'e'occliisal surfacesof the lower teeth, the point of emie'nce of the occlusal surfaces of the lower teeth being above the buccal and lingual ridges of the teeth and being founded for contact with the tips of the mechanical cusps on the upper teeth.

6. The combination with upperand l-owe'rdentures, each denture having artificial posterior teeth, the posterior teeth of the upper denture having armoured mechanical semi-globular cusps formed on their occlusal surfaces, and the'posteriorteeth of the lower denture having armoured lingual and buccal cusps and armoured buccolingual ridges adapted to span the mechanical cusps of the upper teeth during mandibular motion.

7. In a group of artificial posterior teeth including complementary upper and lower teeth having meeting occlusal surfaces, the construction in which each upper tooth has its occlusal surface transversely concave in a buccal-lingual direction and has buccal and lingual cusps and spaced apart mechanical cusps of rounded shape disposed between said buccal and lingual cusps, and each lower tooth has its occlusal surface transversely convex in a buccal-lingual direction and has a buccal and a lingual ridge and a transverse ridge extending between the buccal and lingual ridges between the mesial and distal borders of the complementary occlusal surface, the ridges on each lower tooth having a width at least as great as the distance between adja cent mechanical cusps on the complementary upper tooth.

8. In a group of artificial posterior teeth including complementary upper and lower teeth having meeting occlusal surfaces, the construction in which each upper tooth has its occlusal surface transversely concave in a buccal-lingual direction and has buccal and lingual cusps and mechanical cusps of rounded shape spaced apart in both a buccal-lingual and a distal-mesial direction between said buccal and lingual cusps, and each lower tooth has its occlusal surface transversely convex in a buccal-lingual direction and has a buccal and a lingual ridge and a transverse ridge extending between the buccal and lingual ridges between the mesial and distal borders of the complementary occlusal surface, the ridges on each lower tooth having a width at least as great as the distance between adjacent mechanical cusps on the complementary upper tooth.

9. In a group of artificial posterior teeth including complementary upper and lower teeth having meeting occlusal surfaces, the construction in which each upper tooth has its occlusal surface transversely concave in a buccal-lingual direction and has buccal and lingual cusps and spaced apart mechanical cusps of rounded shape disposed between said buccal and lingual cusps, and each lower tooth has its occlusal surface transversely convex in a buccal-lingual direction and has a buccal and a lingual ridge and a transveres ridge extending between the buccal and lingual ridges between the mesial and distal borders of the complementary ocolusal surface, the ridges on each lower tooth having a width at least as great as the distance between adjacent mechanical cusps on the complementary upper tooth, the buccal cusp on each upper tooth having a greater eminence than any other cusp on the [same tooth and the lingual ridge on each lower tooth having a greater eminence than the corresponding buccal ridge] same tooth and the buccal ridge on each lower tooth having a greater eminence than the corresponding lingual ridge.

10. In a group of artificial posterior teeth including complementary upper and lower teeth having meeting occlusal surfaces, the construction in which each upper tooth has its occlusal surface transversely concave in a buccal-lingual direction and has buccal and lingual cusps and spaced apart mechanical cusps of rounded shape disposed between said buccal and lingual cusps, and each lower tooth has its occlusal surface transversely convex in a buccal-lingual direction and has a buccal and a lingual ridge and a trans- Verse ridge extending between the buccal and lingual ridges between the 'mesial and distal borders of the complementary occlusal surface, the ridges on' each lower tooth having a width at least as great as the distance between adjacent mechanical cusps on the complementary upper tooth, the buccal cusp on each upper tooth hav ing a greater eminence than any other cusp on [the same tooth and the lingual ridge on each lower tooth having a greater eminence than the corresponding buccal ridge with the point of max-] the same tooth and the buccal ridge on each lower tooth having a greater eminence than the corresponding lingual ridge with the point of maximum eminence on each lower tooth located on the buccal-lingual ridges of such tooth.

ROBERT J. DONAVAN.

REFERENCES CITED The following references are of record in the file of this patent or the original patent:

UNITED STATES PATENTS Number Name Date 1,367,477 Homer Feb. 1, 1921 1,987,712 Schroder et a1. Jan. 15, 1935 2,548,956. Dickson Apr. 1'7, 1951 2,549,636 Raber Apr. 17, 1951 FOREIGN PATENTS Number Country Date 17,263 Great Britain Aug. 28, 1901 

